Communication link with non-intrusive expansion capability

ABSTRACT

Systems and methods are described for communications links with non-intrusive expansion capability. A first splitter combiner switches form a shut state to a bypass state when a second headend output is communicatively coupled to a first upstream input and a second headed output is communicatively coupled to a first downstream output. The first splitter combiner is then switchable back to the shut state from the bypass state when the either the second headend output is communicatively decoupled from the first upstream input or the second headend input is communicatively decoupled from the first downstream output. The systems and methods provide advantages because a communication network can be equipped for non-intrusive expansion of the network.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to the field of communication networks.More particularly, the invention relates to the use ofsplitter-combiners in ring communication networks.

2. Discussion of the Related Art

Communication nodes are designed and used for point to pointcommunications over a network. A communications node is a transmittingand receiving (TX/RX) source.

Stringing a plurality of nodes together into a ring network is wellknown to those skilled in the art of communications. What is also wellknown is that an interruption in communication service can be bothinconvenient and costly.

For instance, a conventional ring network is shown in FIG. 1, where aphysical bus logical ring is depicted with three nodes 110, 120, 130communicatively coupled to a headend. Each of the nodes 110-130 includesa data drop/add device 125. Node 110 is physically connected to node 120with a pair of optical fibers 140. Node 120 is physically coupled tonode 130 with a further pair of optical fibers 150. FIG. 1 indicates bydashed line segments that additional nodes may be positioned betweennodes 120 and 130.

Another instance of a conventional ring network is shown in FIG. 4,where a ring architecture is depicted with three nodes 410, 420, 430communicatively coupled to a headend. As above, each of the nodes410-430 includes the data drop/add device 125. However, node 420 isphysically connected to node 410 with a single optical fiber 440.Similarly, node 430 is physically coupled to node 420 with a singleoptical fiber 450. FIG. 4 indicates by dashed line segments thatadditional nodes may be positioned along fiber 450 between nodes 420 and430.

A disadvantage of either of the instances shown in FIGS. 1 and 4 is thata break one of the optical fiber lines can prevent all of the nodes frombidirectionally communicating with the headend. Therefore, what isrequired is solution that provides the network with at least someprotection in the event of a break in one of the fiber lines.

One approach to providing some protection in the event of a break in oneof the fibers in the past has been to connect the nodes together withredundant parallel fibers. A break in one fiber can then be overcomethrough the use of a parallel redundant fiber. However, a disadvantageof this approach has been relatively high cost. Therefore, what is alsoneeded is a solution that provides some protection in the event of afiber break in a more cost-effective manner.

Another problem with this technology has been that expansion of a ringnetwork requires interruption of communication services. Adding a nodeto the ring requires that the ring be broken, at least temporarily, sothat the new node can be inserted into the ring. This break in the ringcan prevent all of the nodes from bidirectionally communicating with theheadend until the installation is complete. In many commercial settings,such a temporary interruption to install additional nodes isunacceptable. Therefore, what is also required is a solution thatpermits the network to be expanded without interrupting communicationservice.

Another problem with this technology has been failure of activeequipment along the ring. If one of the data drop/add devices fails, allof the nodes can be prevented from bidirectionally communicating withthe headend. Therefore, what is also required is a solution thatprovides protection in the event of active equipment failure.

Heretofore, the requirement(s) of protection in the event of a linebreak, expandability without interruption, and protection in the eventof active equipment failure, referred to above have not been fully met.What is needed is a solution that addresses at least one, and preferablyall, of these requirements. The invention is directed to meeting theserequirements, among others.

SUMMARY OF THE INVENTION

A goal of the invention is to simultaneously satisfy the above-discussedrequirements of network protection in the event of a line break,expandability without communications interruption, and networkprotection in the event of active equipment failure which, in the caseof the prior art, are not satisfied, much less simultaneously satisfied.Another goal of the invention is to satisfying one or two of theserequirements.

One embodiment of the invention is based on an apparatus, comprising acommunications link, said communications link including asplitter-combiner communicatively coupled to a headend, saidsplitter-combiner including: a signal splitter communicatively coupledto a headend input and communicatively coupled to a downstream output;and signal combiner communicatively coupled to said signal splitter,communicatively coupled to an upstream input, and communicativelycoupled to a headend output. Another embodiment of the invention isbased on a method, comprising deploying a communications link at least aportion of which is protected against signal conductor failure, whereindeploying includes providing said communications link with asplitter-combiner that is communicatively coupled to a headend. Anotherembodiment of the invention is based on a method, comprising deploying acommunications link with non-intrusive expansion capability, whereindeploying includes providing said communications link with asplitter-combiner communicatively coupled to a headend.

Another embodiment of the invention is based on an apparatus, comprisinga communications link, said communications link including asplitter-combiner communicatively coupled to a headend, saidsplitter-combiner including: a signal splitter communicatively coupledto a headend input and communicatively coupled to a downstream output;and signal combiner communicatively coupled to said signal splitter,communicatively coupled to an upstream input, and communicativelycoupled to a headend output; and a data drop/add device communicativelycoupled to said downstream output and communicatively coupled to saidupstream input. Another embodiment of the invention is based on anapparatus, comprising a communications link, said communications linkincluding a first splitter-combiner communicatively coupled to aheadend, said first splitter-combiner including: a first signal splittercommunicatively coupled to a first headend input and communicativelycoupled to a first downstream output; and a first signal combinercommunicatively coupled to said first signal splitter, communicativelycoupled to a first upstream input, and communicatively coupled to afirst headend output; a data drop/add device communicatively coupled tosaid first downstream output and communicatively coupled to said firstupstream input; a second splitter-combiner communicatively coupledbetween said first headend input and said headend, said secondsplitter-combiner including: a second signal splitter communicativelycoupled to said headend and communicatively coupled to a seconddownstream output; and a second signal combiner communicatively coupledto said second signal splitter, communicatively coupled to a secondupstream input, and communicatively coupled to said first headend input.Another embodiment of the invention is based on a method, comprisingdeploying a communication link, at least a portion of which is protectedagainst active equipment failure, that includes a splitter-combinercommunicatively coupled between a data drop/add device and a headend.

These, and other goals and embodiments of the invention will be betterappreciated and understood when considered in conjunction with thefollowing description and the accompanying drawings. It should beunderstood, however, that the following description, while indicatingpreferred embodiments of the invention and numerous specific detailsthereof, is given by way of illustration and not of limitation. Manychanges and modifications may be made within the scope of the inventionwithout departing from the spirit thereof, and the invention includesall such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

A clear conception of the advantages and features constituting theinvention, and of the components and operation of model systems providedwith the invention, will become more readily apparent by referring tothe exemplary, and therefore nonlimiting, embodiments illustrated in thedrawings accompanying and forming a part of this specification, whereinlike reference characters (if they occur in more than one view)designate the same parts. It should be noted that the featuresillustrated in the drawings are not necessarily drawn to scale.

FIG. 1 illustrates a schematic view of a conventional physical bus,logical ring, appropriately labeled “PRIOR ART”.

FIG. 2 illustrates a schematic view of a physical bus, logical ring witheach node includes a splitter-combiner which can provide fiberprotection and/or non-intrusive expansion, representing an embodiment ofthe invention.

FIG. 3 illustrates the physical bus, logical ring of FIG. 2 after thenon-intrusive addition of a fourth node having a splitter-combiner,representing an embodiment of the invention.

FIG. 4 illustrates a schematic view of a conventional ring architecture,appropriately labeled “PRIOR ART”.

FIG. 5 illustrates a schematic view of a ring architecture with eachnode including a splitter-combiner, which can provide active equipmentprotection, representing an embodiment of the invention.

FIG. 6 illustrates a more detailed schematic view of the A/D devicesdepicted in FIGS. 1-5, appropriately labeled “PRIOR ART”.

FIG. 7 illustrates a schematic view of a physical bus, logical ringarchitecture with each A/D node including two splitter-combiners, afirst of which can provide active equipment protection and a second ofwhich can provide fiber protection and/or non-intrusive expansion,representing a combined embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The invention and the various features and advantageous details thereofare explained more fully with reference to the nonlimiting embodimentsthat are illustrated in the accompanying drawings and detailed in thefollowing description of preferred embodiments. Descriptions of wellknown components and processing techniques are omitted so as not tounnecessarily obscure the invention in detail.

The context of the invention includes communication networks. Expectedapplications include physical bus, logical rings. Expected applicationsalso include ring architectures.

The invention can include placing a splitter in the transmitting path ofa node and another splitter in the receiving path of the same node. Inthe case of optical signal splitting, the splitters can be readilycommercially available fiber optic tap couplers. In the case ofelectrical signal splitting, the splitters can be simple Y branches. Ineither case, two of the splitters can be coupled together to compose asplitter-combiner. In this coupled configuration one of the splittersfunctions as a combiner. The splitter-combiner in-turn defines a shuntand a bypass.

By providing signals combined from the bypass with a gain of fromapproximately 10 dB to approximately 20 dB relative to signals combinedfrom the shunt, a switching functionality is provided by thesplitter-combiner. If a signal is present on the bypass, this bypasssignal will be detected. If no signal (or only a very weak signal) ispresent on the bypass, the shunt signal will be detected. It isimportant to appreciate that signals being transmitted along the shuntare overwhelmed by signals being transmitted along the bypass, if thelater are present.

The splitters that compose the splitter-combiner can be optical in thecase of an optical communications network. Alternatively, thesesplitters can be electrical in the case of an electrical communicationsnetwork. Further, these splitters could even be vibrational in the caseof an acoustical communications network. Other types of splitters couldbe used.

Preferred embodiments of the invention can use a passivesplitter-combiner. In the case of an optical network, a passive splittercombiner can include two fiber optic couplers. The use of a passivesplitter-combiner confers major advantages. There is no need formechanical or electrical switching. There is no need for faultdetection. There is no need for monitoring. There are fewer componentscompared to an active device. There is no switch to fail. There is noswitching time.

The invention can include protecting at least a portion of a networkagainst failure of signal connection lines. For example, given aphysical bus, logical ring, each node can be provided with asplitter-combiner. If a signal connection line fails, thesplitter-combiner that is RX relative the failed line will switch todetecting signals from the shunt. In this way, at least part of thenetwork can be protected from the affect of the failed line. This can betermed fiber protection.

The splitter-combiners do not have to be located in the same chassis asthe data drop/add devices, or even the same nodes. The splittercombiners can be located in-between nodes. Preferred embodiments of theinvention use a passive splitter-combiner device to shunt thecommunications route around the failed line.

Referring to FIG. 2, a physical bus, logical ring is depicted with afirst node 210, a second node 220 and a third node 230, each of whichincludes a data drop/add device 125. FIG. 2 indicates by dashed linesegments that additional nodes may be positioned between nodes 220 and230.

A splitter-combiner 250 is located within each of the nodes 210-230.Each of the splitter-combiners 250 includes a signal splitter 260 and asignal combiner 270 (see the detail numbers relating to thesplitter-combiner in the second node 220). The signal combiner 270 iscommunicatively coupled to the signal splitter 260.

Each of the signal splitters 260 is communicatively coupled to a headendinput 262 (see the detail numbers relating to the signal splitter in thethird node 230). Each of the signal splitters 260 is communicativelycoupled to a downstream output 264.

Each of the signal combiners 270 is communicatively coupled to anupstream input 272 (see the detail numbers relating to the signalcombiner in the third node 230). Each of the signal combiners 270 iscommunicatively coupled to a headend output 274.

The path (connection) between the downstream output 264 and the upstreaminput 272 can be termed a bypass. The other path, typically a shorterpath, between the signal splitter 250 and the signal combiner 260 can betermed a shunt.

In this embodiment, the data drop/add device 125 of each node iscommunicatively coupled to the headend output 274 of the correspondingsignal combiner 270. Data flow is from the signal combiner to the datadrop/add device.

By providing the third node 230 with its splitter-combiner, an importantexpansion feature is enabled. The addition of another node to the thirdnode 230 will be discussed below in more detail with regard to FIG. 3.

The invention can include adding a node to a network withoutinterrupting service to other nodes on the network. For example, given aphysical bus, logical ring, the last (terminal) node on the bus can beprovided with a splitter-combiner that will initially detect signalsfrom the shut. The additional node would then be connected to thesplitter-combiner. The additional node would then be the new terminalnode on the physical bus, logical ring. Upon connecting the additionalnode, the splitter-combiner in what was the terminal node will switch todetecting signals from the bypass. This can be termed non-intrusiveexpansion.

As above, the splitter-combiners do not have to be located in the samechassis as the data drop/add devices, or even the same nodes. Preferredembodiments of the invention use a passive splitter-combiner device tobypass the communications route to the new terminal node.

Referring to FIG. 3, a fourth node 340, which includes another datadrop/add device 125, has been connected to the third node 230. Thesignal combiner in the fourth node 340 is communicatively connected tothe upstream input of the third node 230. Similarly, the signal splitterin the fourth node 340 is communicatively connected to the downstreamoutput of the third node 230.

Of course, additional nodes may be added to the fourth node 340. Byproviding the fourth node 340 with its splitter-combiner, the feature ofnon-intrusive expansion is still enabled.

The invention can include protecting at least a portion of a ringnetwork against failure of active equipment. For example, an activeequipment device can be isolated from the rest of the network byproviding the node with which the active device is associated with asplitter-combiner. If the active device fails, the associatedsplitter-combiner will switch to detecting the shunt signal, therebybypassing the failed device. This can be termed active equipmentprotection.

Again, although it can be advantageous to co-locate thesplitter-combiners with the data drop/add devices, thesplitter-combiners do not have to be located in the same chassis as thedata drop/add devices or even the same nodes. Since active equipment canfail for a number of reasons, notably power failure, preferredembodiments of the invention use a passive splitter-combiner device toshunt the communications route around the failed active device.

Referring to FIG. 5, a ring architecture is shown with a first node 510,a second node 520 and a third node 530, each of which includes a datadrop/add device 125. FIG. 5 indicates by dashed line segments thatadditional nodes may be positioned between nodes 520 and 530.

In this embodiment, the data drop/add device 125 of each node iscommunicatively coupled to the upstream input 272 of the correspondingsignal combiner 270. The data drop/add device 125 of each node is alsocommunicatively coupled to the downstream output 264 of thecorresponding signal splitter 260. Data flow is from the downstreamoutput 264 of the corresponding signal splitter 260 to the data drop/adddevice 125 and then to the upstream input 272 of the correspondingsignal combiner 270.

Referring now to FIG. 6, the data drop/add device 125 is depicted in amore detailed manner. The data drop/add device 125 includes an opticalreceiver 610 (ORX). The optical receiver 610 can be anoptical-to-electronic transducer such as a charge-coupled device.Electrical circuit 620 is coupled to the optical receiver 610. Anoptical transmitter 630 (OTX) is coupled to the circuit 620. The opticaltransmitter can be an electronic-to-optical transducer such as a laserdiode.

The invention can also include combining two or more of fiberprotection, non-intrusive expansion, and/or active device protection. Tocombine these functionalities, two of the splitter-combiners can bejoined together to form a combined device. Again, preferred embodimentsof the invention use passive splitter-combiners. However, all aspects ofthe invention can be implemented with active splitter-combiners.

Referring to FIG. 7, a physical bus, logic ring is depicted with a firstnode 710, a second node 720 and a third node 730, each of which includesa data drop add device 125. Of course, additional nodes may be locatedbetween the depicted nodes.

In this embodiment, each of the nodes includes two splitter-combers 250.By coupling the headend output 274 of the first splitter-combiner to theheadend input 262 of the second splitter combiner both of the featuresof fiber protection and active equipment protection are enabled. Byproviding the third node 730 with splitter-combiner, the feature ofnon-intrusive expansion is enabled.

The invention can also be included in a kit. The kit can include some,or all, of the components that compose the invention. More specifically,the kit can include the splitter-combiner and other components of theinvention. The kit can also include a splicing equipment and suppliesfor retrofitting existing nodes with the invention. The kit can containa computer program. The kit can also contain instructions for practicingthe invention and apparatus for carrying out the invention. Unlessotherwise specified, the components (and apparatus and/or instructions)of the kit can be the same as those used in the invention.

The invention can also utilize data processing methods that transformsignals from one state to another. For example, the invention can becombined with instrumentation to obtain state variable information onthe detected signal(s) to actuate interconnected discrete hardwareelements. For instance, the invention can include monitoring theswitching state of the splitter-combiners and reporting their state tothe headend for recordation as diagnostic data. Further, the inventioncan even include measuring the relative signal attenuation between thebypass and shunt to change the split ratio of the signal splittersand/or signal combiners with variable filter, polarizers and/orrefractive index devices, thereby lowering detected noise from the shuntduring bypass operation while simultaneously maintaining sufficient shutsensitivity to meet the needs of a contingent switching event.

The term approximately, as used herein, is defined as at least close toa given value (e.g., preferably within 10% of, more preferably within 1%of, and most preferably within 0.1% of). The term coupled, as usedherein, is defined as connected, although not necessarily directly, andnot necessarily mechanically. The term deploying, as used herein, isdefined as designing, building, shipping, installing and/or operating.The term program or phrase computer program, as used herein, is definedas a sequence of instructions designed for execution on a computersystem. A program may include a subroutine, a function, a procedure, anobject method, an object implementation, an executable application, anapplet, a servlet, a source code, an object code, and/or other sequenceof instructions designed for execution on a computer system.

The particular manufacturing process used for fabricating thesplitter-combiner should be inexpensive and reproducible. Conveniently,the splitter-combiner of the invention can be fabricated using anysplicing method to join two Y branches, either optical or electrical. Inthe case of optical branches (e.g., tap couplers) it is preferred thatthe process be an optical butt splicing technique. For the manufacturingoperation, it is an advantage to employ a UV light curing, guide tubetechnique.

However, the particular manufacturing process used for fabricating thesplitter-combiner is not essential to the invention as long as itprovides the described functionality. Normally those who make or use theinvention will select the manufacturing process based upon tooling andenergy requirements, the expected application requirements of the finalproduct, and the demands of the overall manufacturing process.

While not being limited to any particular performance indicator ordiagnostic identifier, preferred embodiments of the invention can beidentified one at a time by testing for the presence of sufficientsignal strength differential at the headend output of thesplitter-combiner. At the headend output of the splitter-combiner, thedifference in relative strength between signal(s) entering the head endinput and signal(s) entering the upstream input should be fromapproximately 10 dB to approximately 20 dB. This difference in relativestrength between the signals can be achieved by selecting the tapcoupling ratios (split ratios) of the signal splitter and the signalcombiner. This difference in relative strength can also be achieved byadjusting the amplitude of signals entering the headend input and theamplitude of signals entering the upstream input. The test for thepresence of sufficient signal strength differential can be carried outwithout undue experimentation by the use of a simple and conventionalsignal strength meter experiment.

EXAMPLES

Specific embodiments of the invention will now be further described bythe following, nonlimiting examples which will serve to illustrate insome detail various features of significance. The examples are intendedmerely to facilitate an understanding of ways in which the invention maybe practiced and to further enable those of skill in the art to practicethe invention. Accordingly, the examples should not be construed aslimiting the scope of the invention.

Example 1

A physical bus, logical ring, can provide the fiber protection andnon-intrusive expansion functionalities where each add/drop (A/D) nodeincludes a splitter-combiner. The splitter-combiner can include a signalsplitter where approximately 5% of the signal energy is deflected to theshunt and approximately 95% of the signal energy is directed toward thebypass. Suitable fiber optic couplers with this output port ratio arereadily commercially available from E-TEK Dynamics, Inc. (models SWBCand/or SMFC); and Amphenol (part no. 945-271-C100). Thesplitter-combiner can include a signal combiner where approximately 50%of the combined signal energy is derived from the shunt, andapproximately 50% of the combined signal energy is derived from thebypass. Suitable fiber optic couplers are readily commercially availablefrom JDS Fitel (AC Series); E-TEK Dynamics, Inc. (models SWBC and/orSMFC); and Amphenol (part nos. 945-130-1000, 945-131-1000, 945-132-1000,945-170-1000, 945-171-1000 and/or 945-172-1000).

Example 2

A physical bus, logical ring, can provide the fiber protection andnonintrusive expansion functionalities where each add/drop (A/D) nodeincludes a splitter-combiner. The splitter-combiner can include a signalsplitter where approximately 10% of the signal energy is deflected tothe shunt and approximately 90% of the signal energy is directed towardthe bypass. Suitable fiber optic couplers are readily commerciallyavailable from JDS Fitel (AC Series); Amphenol (part nos. 945-130-2000,945-131-2000, 945-132-2000, 945-170-2000, 945-171-2000 and/or945-172-2000). The splitter-combiner can include a signal combiner whereapproximately 10% of the combined signal energy is derived from theshunt, and approximately 90% of the combined signal energy is derivedfrom the bypass.

Example 3

The active equipment functionality can be provided by a ringarchitecture where each add/drop (A/D) node includes asplitter-combiner. The splitter-combiner can include a signal splitterwhere approximately 10% of the signal energy is deflected to the shuntand approximately 90% of the signal energy is directed toward thebypass. The splitter-combiner can include a signal combiner whereapproximately 10% of the combined signal energy is derived from theshunt, and approximately 90% of the combined signal energy is derivedfrom the bypass.

Practical Applications of the Invention

A practical application of the invention that has value within thetechnological arts is the non-intrusive expansion of communicationnetworks, such as adding a data drop/add node to a logical loop.Further, the invention is useful in conjunction with controlling thespread of damage from failure of passive components in a communicationsnetwork (such as broken optical fibers and/or severed coaxial cables),or in conjunction with controlling the spread of damage from failure ofactive components (such as data drop/add nodes and/or repeaters), or thelike. There are virtually innumerable uses for the invention, all ofwhich need not be detailed here.

All the disclosed embodiments of the invention described herein can berealized and practiced without undue experimentation. Although the bestmode of carrying out the invention contemplated by the inventors isdisclosed above, practice of the invention is not limited thereto.Accordingly, it will be appreciated by those skilled in the art that theinvention may be practiced otherwise than as specifically describedherein.

For example, the individual components need not be assembled in thedisclosed configuration, but could be assembled in virtually anyconfiguration. Further, the individual components need not be fabricatedfrom the disclosed materials, but could be fabricated from virtually anysuitable materials. Further, although the splitter-combiner describedherein can be a physically separate module, it will be manifest that thesplitter-combiner may be integrated into the apparatus with which it isassociated. Furthermore, all the disclosed elements and features of eachdisclosed embodiment can be combined with, or substituted for, thedisclosed elements and features of every other disclosed embodimentexcept where such elements or features are mutually exclusive.

It will be manifest that various additions, modifications andrearrangements of the features of the invention may be made withoutdeviating from the spirit and scope of the underlying inventive concept.It is intended that the scope of the invention as defined by theappended claims and their equivalents cover all such additions,modifications, and rearrangements.

The appended claims are not to be interpreted as includingmeans-plus-function limitations, unless such a limitation is explicitlyrecited in a given claim using the phrase “means for.” Expedientembodiments of the invention are differentiated by the appendedsubclaims.

What is claimed is:
 1. An apparatus, comprising: a firstsplitter-combiner coupleable to a headend, said first splitter-combinerincluding: a first signal splitter communicatively coupled to a firstheadend input and communicatively coupled to a first downstream output;and a first signal combiner communicatively coupled to said first signalsplitter via a first shunt, communicatively coupled to a first upstreaminput, and communicatively coupled to a first headend output; and asecond splitter-combiner communicatively coupleable to the firstsplitter-combiner, said second splitter-comber including: a secondsignal splitter communicatively coupled to a second headend input andcommunicatively coupled to a second downstream output; and a secondsignal combiner communicatively coupled to said second signal splittervia a second shunt, communicatively coupled to a second upstream input,and communicatively coupled to a second headend output, wherein thefirst splitter combiner switches from a shut state to a bypass statewhen the second headend output is communicatively coupled to the firstupstream input and the second, headend input is communicatively coupledto the first downstream output, signals from the first headend inputswitched to the second headend input and signals from the second headendoutput switched to the first headend output and wherein the firstsplitter combiner is then switchable back to the shut state from thebypass state when the either the second headend output iscommunicatively decoupled from the first upstream input or the secondheadend input is communicatively decoupled from the first downstreamoutput, signals from the first headend input switched to the firstheadend output via the shunt.
 2. The apparatus of claim 1, wherein saidfirst splitter-combiner is a first passive device and said secondsplitter-combiner is a second passive device.
 3. The apparatus of claim1, wherein said second splitter-combiner defines a terminal node of acommunications link.
 4. The apparatus of claim 1, further comprisinganother splitter-combiner communicatively coupleable to the secondsplitter-combiner, said another splitter-comber including: anothersignal splitter communicatively coupled to another headend input andcommunicatively coupled to another downstream output; and another signalcombiner communicatively coupled to said another signal splitter viaanother shunt, communicatively coupled to another upstream input, andcommunicatively coupled to another headend output, wherein the secondsplitter combiner switches from shut to bypass when the another headendoutput is communicatively coupled to the second upstream input and theanother headend input is communicatively coupled to the seconddownstream output and wherein the second splitter combiner is thenswitchable back to shut from bypass when the either the another headendoutput is communicatively decoupled from the second upstream input orthe another headend input is communicatively decoupled from the seconddownstream output.
 5. The apparatus of claim 3, wherein all nodes thatare included in said communications link include a splitting-combiningcapability.
 6. The apparatus of claim 1, further comprising a datadrop/add device communicatively coupled between said first upstreaminput and said second headend output.
 7. The apparatus of claim 6,wherein said data drop/add device includes an optical-to-electronictransducer coupled to said second headend output and anelectronic-to-optical transducer coupled to said first upstream input.8. The apparatus of claim 1, further comprising an optical fibercommunicatively coupled between said first upstream input and saidsecond headend output, said first signal splitter includes a firstoptical beam splitter, said first signal combiner include a firstoptical beam combiner, said second signal splitter includes a secondoptical beam splitter and said second signal combiner includes a secondoptical beam combiner.
 9. The apparatus of claim 1, further comprising acoaxial cable communicatively coupled between said first upstream inputand said second headend output, said first signal splitter includes afirst electrical splitter circuit, said first signal combiner includes afirst electrical combiner circuit, said second signal splitter includesa second electrical splitter circuit and said second signal combinerincludes a second electrical combiner circuit.
 10. A method, comprisingdeploying a communications link with non-intrusive expansion capabilitywherein deploying includes: providing a first splitter-combinercoupleable to a headend, said first splitter-combiner including: a firstsignal splitter communicatively coupled to a first headend input andcommunicatively coupled to a first downstream output; and a first signalcombiner communicatively coupled to said first signal splitter via afirst shunt, communicatively coupled to a first upstream input, andcommunicatively coupled to a first headend output; providing a secondsplitter-combiner communicatively coupleable to the firstsplitter-combiner, said second splitter-comber including: a secondsignal splitter communicatively coupled to a second headend input andcommunicatively coupled to a second downstream output; and a secondsignal combiner communicatively coupled to said second signal splittervia a second shunt, communicatively coupled to a second upstream input,and communicatively coupled to a second headend output; and couplingcommunicatively the second headend output to the first upstream inputand the second headend input to the first downstream output, whereinfirst splitter combiner switches from a shut state to a bypass statewhen the second headend output is communicatively coupled to the firstupstream input and the second headend input is communicatively coupledto the first downstream output, signals from the first headend inputswitched to the second headend input and signals from the second headendoutput switched to the first headend output and wherein the firstsplitter combiner is then switchable back to the shut state from thebypass state when the either the second headend output iscommunicatively decoupled from the first upstream input or the secondheadend input is communicatively decoupled from the first downstreamoutput, signals from the first headend input switched to the firstheadend output via the shunt.
 11. The method of claim 10, furthercomprising further comprising providing another splitter-combinercommunicatively coupleable to the second splitter-combiner, said anothersplitter-comber including: another signal splitter communicativelycoupled to another headend input and communicatively coupled to anotherdownstream output; and another signal combiner communicatively coupledto said another signal splitter via another shunt, communicativelycoupled to another upstream input, and communicatively coupled toanother headend output, wherein the second splitter combiner switchesfrom shut to bypass when the another headend output is communicativelycoupled to the second upstream input and the another headend input iscommunicatively coupled to the second downstream output and wherein thesecond splitter combiner is then switchable back to shut from bypasswhen the either the another headend output is communicatively decoupledfrom the second upstream input or the another headend input iscommunicatively decoupled from the second downstream output.
 12. Themethod of claim 10, further comprising monitoring a switching state ofsaid first splitter-combiner.
 13. The method of claim 12, furthercomprising reporting said switching state to said headend.
 14. Themethod of claim 13, further comprising recording said switching state asdiagnostic data.
 15. The method of claim 10, further comprisingmeasuring a relative signal attenuation between a first detected bypasssignal and a first detected shunt signal.
 16. The method of claim 15,further comprising changing a split ratio of the firstsplitter-combiner.